package three;

public class 三十一递归与迭代 {
    public static void main(String[] args) {
        long d1 = System.currentTimeMillis();
        System.out.printf("%d阶乘的结果:%s%n", 10, factorial(10));
        long d2 = System.currentTimeMillis();
        System.out.printf("递归费时：%s%n", d2-d1);  //耗时：32ms

        long d3 = System.currentTimeMillis();
        int a = 10;
        int result = 1;
        while (a > 1) {
            result *= a * (a - 1);
            a -= 2;
        }
        long d4 = System.currentTimeMillis();
        System.out.println(result);
        System.out.printf("普通循环费时：%s%n", d4 - d3);
    }
    /** 求阶乘的方法*/
    static long  factorial(int n){
        if(n==1){//递归头
            return 1;
        }else{//递归体
            return n*factorial(n-1);//n! = n * (n-1)!
        }

    }
}
